The invention relates to the melting of thermo-plastic materials and, more particularly, relates to an improved apparatus and method for recovering liquid sulphur from crude elemental sulphur in rock, pellet, granular, flaked, slated or powdered form. In the prior art, sulphur has been typically melted in tanks, vats or pits having heating coils. A continuous supply of coarsely divided sulphur was fed into the melting containers and the resultant slurry was vigorously agitated at a temperature above the melting point of sulphur to accelerate the remelt rate. These melting devices and methods were inefficient and required substantial labor for operation and maintenance, and required considerable capital investment.
In these devices problems were caused by entrained moisture in the solid sulphur which resulted in violent foaming, reduced capacity, and frequent shutdown time was necessary to remove solid rock-like sediments from the melting devices. Because these prior art methods relied solely on applying heat to the solid indirectly through the liquid, a low heat transfer coefficient, U, existed and resulted in the requirement for mechanical agitation of the solid-liquid sulphur in order to operate at practical rates. The present invention eliminates the need for agitation equipment, the violent foaming, frequent cleaning, and the uneconomical heat transfer operation.
Other prior art devices have structures within the solid and liquid sulphur areas that increase resistance to solid and liquid flow. Such devices also permit some solid sulphur to be discharged with the liquid.